Multiple switches between vegetative and reproductive growth in annual plants

A model of growth and reproduction in annual plants was developed by Cohen (1971, J. Theor. Biol.33, 299–307) to determine the allocation strategy which maximizes seed yield. The model divides the plant into vegetative and reproductive parts and predicts that yield is maximized by a strategy consisting of a switch from purely vegetative to strictly reproductive growth. We generalize Cohen's model to include vegetative and reproductive loss terms. Both growth and loss rates are allowed to vary with time. Using optimal control theory we find that seed yield is maximized by a strategy consisting of multiple switches between vegetative and reproductive growth, for certain ranges of the model parameters. In natural systems a predictable vegetative loss burst may be necessary to promote multiple switches.     

A review of biomechanical models

This paper surveys biomechanical models of the nonimpact type, involving the musculo-skeletal system. Models of bones, joints and body segments, including human gait and motion of the whole body are discussed. In particular, stress analysis of bone, calculation of ligament and muscle forces across joints and the kinetics and kinematics of locomotion are discussed. The models are described in terms of the method of formulation, the method of solution and the realism of the results obtained. There is a need for more data on material properties of various body tissues and more experimental research to develop techniques for validating many of the models. Further work on the selection of appropriate objective functions for indeterminate problems is also required.     

A rapid bactometer method for screening of biocides against sulfate-reducing bacteria

A rapid and efficient bactometer method was developed for screening biocides against sulfate-reducing bacteria. The method is based on impedance microbiology principles and uses double-layer API (American Petroleum Institute) agar medium supplemented with 0.1% sodium thioglycolate as a reducing agent. Compared to the conventional API procedure, which requires 28 days, the present technique takes only 1 day to obtain test results. Excellent linear correlation (r=–0.98) was found between the impedance detection time and log initial cell concentration. The results of the bactometer test were comparable to that of the API bottle test.